[FSSDK-11090] remove unused plugins directory #982

Job	Run time
crossbrowser_and_umd_unit_tests	6h 0m 14s
lint	1m 1s
unit_tests (16)	1m 48s
unit_tests (18)	1m 34s
unit_tests (20)	1m 28s
unit_tests (22)	1m 22s
fullstack_production_suite / test	4s
integration_tests / test	4s
lint_markdown_files / lint	1m 26s
Coveralls coverage	2s
	6h 9m 3s

Provide feedback